Catalyst compositions

ABSTRACT

Catalytic compositions comprising up to about 50 weight percent ZSM-5 zeolite dispersed in an attrition resistant, porous inorganic oxide matrix selected from silica-alumina cogels, silica, alumina and silica alumina sol bound clay. The compositions are combined with zeolitic containing catalytic cracking catalysts and used to convert residual and/or gas oil hydrocarbon feedstocks into lower molecular weight products that include high octane gasoline fractions.

This is a continuation of application Ser. No. 819,777, filed Jan. 16,1986, now abandoned.

The present invention relates to the manufacture of catalysts, and moreparticularly to the manufacture and use of zeolite containinghydrocarbon conversion catalysts that are particularly selective for theproduction of high octane gasoline fractions.

Zeolite containing catalysts are used to convert high molecular weighthydrocarbon feedstocks such as residual gas oils to products ofincreased value such as gasoline and diesel fuel. In particular, fluidcatalytic cracking catalysts which contain synthetic faujasite, Type Yzeolites and modified versions thereof such as ultrastable type Yzeolite (USY) and rare earth exchanged type Y zeolite (REY) as well ascalcined rare earth exchanged type Y zeolite (CREY) have been used bythe refining industry for many years.

More recently significant demand has developed for a cc catalyst whichwill produce substantial yields of gasoline which have high inherent(non-leaded) octane rating. In U.S. Pat. Nos. 3,758,403, 3,994,800,4,239,654 and 4,289,606 FCC catalysts which contain USY zeolite as wellas ZSM-5 zeolite have been identified as "octane enhancing catalysts".

While FCC octane enhancing catalysts are available which will producegasoline fractions of increased octane rating, it is often found thatthe existing octane catalysts are expensive and in some instanceslacking in desired activity, and yield producing characteristics. Inparticular, it is frequently observed that decreased gasoline yield istne trade-off for octane enhancement.

It is therefore an object of the present invention to produce animproved octane enhancing catalyst.

It is a further object to provide octane enhancing FCC catalystadditives which may be used with conventional FCC catalysts inconventional FCC units to produce gasoline fractions of enhanced octanerating.

It is another object to provide methods by which octane enhancingcatalysts may be quickly and economically manufactured.

It is still another object to provide a method by which gas-oil andresidual oil FCC feedstocks may be quickly and economically converted toproducts which include cracked gasoline fractions of high inherentoctane rating.

These and still further objects of the present invention will be readilyapparent to one skilled in the art from the following detaileddescription and specific examples.

Broadly, my invention contemplates catalyst compositions which compriseZSM-5 type zeolite combined in an inorganic oxide matrix selected fromthe group consisting of silica-alumina cogels, silica and silica-aluminasols, alumina sols and preferably clay.

More specifically, I have found that an effective octane enhancing FCCcatalyst additive may be obtained by combining from about 5 to about 50weight percent ZSM-5 zeolite with an inorganic oxide matrix such assilica-alumina cogel, silica, silica-alumina, alumina sol bound clay,and mixtures thereof. The matrix component is particularly characterizedby having a (non-zeolite) surface area of about 20 to 400 m² /g and atotal pore volume of from about 0.15 to 0.60 cc/g and more preferably asurface area and pore volume of from about 100 to 400 m² /g and 0.20 to0.60 cc/g respectively.

The ZSM-5 component used in the practice of the present invention iswell known to those skilled in the art, composition and preparation ofwhich is disclosed in U.S. Pat. No. 3,702,886.

The matrix component which is used to combine finely divided ZSM-5component to a cohesive, attrition resistant article with FCC catalystsize is disclosed in U.S. Pat. Nos. 4,499,179 (Silica-Alumina Cogel),3,867,308 and 3,957,689 (Silica and Silica-Alumina Sol Bound Clay), andCanadian No. 967,136 and U.S. Pat. Nos. 4,458,023 and 4,542,118 (AluminaSol-Bound Clay).

In a typical catalyst preparation procedure, the ZSM-5 component isslurried with water, then combined with an aqueous mixture ofsilica-alumina cogel and/or silica, silica-alumina or alumina sol binderand clay (preferably kaolin). The mixture is then spray dried atelevated temperatures from about 150° to 550° C. to obtain catalyticparticles which have an average particle size (APS) of about 50 to 85micrometer. The spray dried product is then washed with water andexchanged with dilute ammonium sulfate solution to lower the soda (Na₂O) content to below about 0.30 weight percent, and preferably to belowabout 0.10 weight percent. The washed product is then dried at atemperature of 150° C. to obtain a catalyst product having a totalvolatic content (TV) of below about 20 percent by weight.

The catalyst additive composition of the present invention may containfrom about 5 to 50, preferably from about 15 to 35 weight percent ZSM-5.The inorganic oxide matrix comprises from about 50 to 95 percent byweight of the overall catalyst, and preferably from about 65 to 85percent by weight. In a particularly preferred embodiment of the presentinvention, the matrix component comprises from about 15 to 85 weightpercent cogel and/or silica, silica-alumina, alumina binder from about 0to 60 weight percent clay.

The octane enhancing catalyst additive of the present invention is usedin conventional fluid catalytic cracking operations wherein aconventional zeolite containing FCC catalyst is contacted with ahydrocarbon feedstock with temperatures on the order of from about 900°to 1400° F. and more preferably from about 900° to 1050° F. to crack thehydrocarbon feedstock to obtain lower molecular weight products such asgasoline and diesel fuel. In a particularly preferred practice of theinvention, the ZSM-5 containing catalyst additive is used in combinationwith a fluid catalytic cracking catalyst which comprises ultrastabletype Y zeolite which is disclosed in U.S. Pat. Nos. 3,293,192 and3,449,070, in combination with a silica or silica-alumina sol/claymatrix which is prepared in accordance with the teachings of U.S. Pat.Nos. 3,867,308, 3,957,689, 4,458,023, 4,542,118 and Canadian 967,136.Preferably, the USY containing octacat catalyst comprises from about 15to 60 weight percent USY and more preferably from about 35 to 45 weightpercent USY. Furthermore, it is contemplated that the ZSM- 5 catalystadditive may be utilized in combination with catalysts which containrare earth stabilized type Y zeolites such as calcined rare earthexchanged type X and Y zeolites (CREX and CREY) which produced inaccordance with the teachings of U.S. Pat. No. Re 28,629.

The ZSM-5 containing catalyst additive used in combination with theconventional FCC catalyst is added to the catalyst inventory of the FCCunit in amounts to produce catalyst mixture which contains from about0.1 to 10 ZSM-5 zeolite, and more preferably from about 1.5 to 5 weightpercent ZSM-5 zeolite and more preferably from about 1.0 to 2.0 weightpercent ZSM-5 zeolite. The feedstocks which are used with the ZSM-5catalyst additives/FCC catalyst combination may comprise gas-oilfeedstocks which boil in the range of from about 600° to 1000° F.,residual feedstocks which contain residual component boiling above about1000° F. in amounts ranging from about 1 percent up to 30 percent byweight of the FCC feedstock. The products which are obtained by thecracking of these feedstocks comprise gasoline fractions which willtypically possess an increased octane rating of from about 1.0 to 6.0RON and 0.2 to 4.0 MON. Furthermore, it is found the catalysts willproduce significant yields of diesel fuel in addition to high octanegasoline fractions with minimal loss of overall liquid yield during theconversion process.

Having described the basic aspects of the invention, the followingexamples are given to illustrate specific embodiments thereof.

EXAMPLE I

An octane enhancing catalyst was prepared which contained 25% ZSM-5, 20%SiO₂.Al₂ O₃ sol binder, 55% kaolin (oxide basis) as follows:

1. A 25% solids slurry was prepared with 5.0 pounds of dry oxide basisZSM-5 in sufficient water to constitute the desired 25% slurry.

2. The slurry in "1" above was acidified to 4.0-4.5 pH using 20% H₂ SO₄.

3. The silica-alumina sol was prepared

containing 4.0 lbs of SiO₂ by reacting continuously a stream of 18° Be'sodium silicate at 70° F. in a centrifugal mix pump with 70° F. acidalum containing 35 g/l Al₂ O₃ and 235 g/l H₂ SO₄ at a discharge pH of3.0-3.1.

4. The silica-alumina sol was collected in a 10 gallon vessel under ahigh shear mixer.

5. The slurry in "2" was added and mixed with the silica-alumina sol in"4".

6. To the slurry in "5" was added with mixing 13.0 lbs of dry poweredkaolin. The kaolin was allowed to fully disperse to a smooth slurry.

7. The slurry from "6" was spray dried to give a 60-70 micron averageparticle size at 12-16% moisture using a wheel atomized parallel flow10' diameter spray dryer.

8. The spray dried catalyst is reslurried in 120°-150° F. watercontaining 0.1 lb ammonium sulfate per pound of oxide basis catalyst.

9. The catalyst slurry from "8" is dewatered and rinsed first with a 5%ammonium sulfate solution at 120° F. and then with sufficient 150° F.water to rinse the cake sulfate free.

10. The catalyst cake from "9" is oven dried at 400° to 12-16% H₂ O toobtain the desired product.

EXAMPLE II

An octane enhancing catalyst was prepared which contained 25% ZSM-5, 78%silica-alumina cogel (25% SiO₂, 75% Al₂ O₃) as follows:

1. A ZSM-5 slurry was prepared as in Example I.1. containing 5.0 lbs drybasis.

2. A silica-alumina cogel was prepared which contained 11.25 lbs Al₂ O₃and 3.75 lbs SiO₂ by continuously reacting a 4% SiO₂ sodium silicatesolution in a centrifugal mix pump with 4% Al₂ O₃ 1.4 mole ratio sodiumaluminate and further reacting this product in a second continuous mixerwith acid alum (35 g/l Al₂ O₃, 235 g/l H₂ SO₄) to obtain a cogel slurryhaving a 10.3-10.5 pH. All solutions were maintained at 80°-90° F.

3. The slurry from "2" was collected and combined with the slurry from"1" and mixed well.

4. The slurry from "3" was dewatered on a belt filter.

5. The dewatered cake from "4" was reslurried with water to facilitatepumping.

6. The slurry from "5" was spray dried, washed, and dried as in ExampleI, steps 7, 8, 9 and 10.

EXAMPLE III

An octane enhancing catalyst was prepared which contained 25% ZSM-5, 15%Al₂ O₃ binder from aluminum chlorhydrol, 60% kaolin (dry oxide basis) asfollows:

1. A ZSM-5 slurry containing 5.0 lbs dry basis was prepared as inExample I.1.

2. The slurry in "1" was acidified to 4.0-4.3 pH with 10% HCl.

3. A slurry was prepared by adding first 13.0 lbs of aluminumchlorhydrol containing 3.0 lbs Al₂ O₃ to a 10 gallon bucket with a highshear agitator and then adding the slurry from "2".

4. To the slurry in "3" was added 14.1 lbs of dry powdered kaolin andallowed to mix until smooth about 5 minutes.

5. The slurry from "4" was spray dried as in Example I, step 7.

6. A portion of the catalyst from "5" was activated for 2 hours at 1000°F. in a muffle furnace to remove volatiles and fix the binder.

EXAMPLE IV

To illustrate the octane increasing properties of the additivecompositions of the present invention, an additive composition of thetype described in Example I (Additive 0) was combined with acommercially available FCC cracking catalyst (Octacat) which comprisesabout 40 percent Ultrastable Type Y zeolite combined withasilica-alumina sol binder and kaolin matrix and used to catalyticallycrack gas oil having a boiling range of about 400° to 1000° F. A summaryof the test results including "Base Case" results obtained using Octacatwithout Additive 0 is set forth in Table A below:

                                      TABLE A                                     __________________________________________________________________________                     BASE CASE                                                                            TEST #1        TEST #2                                                 OCTACAT                                                                              OCTACAT/ADDITIVE "O"                                                                         OCTACAT/ADDITIVE                       __________________________________________________________________________                                           "O"                                    OPERATIONS SUMMARY                                                            CATALYST                                                                      Gas Oil Feed Rate, BPD                                                                         5551   5514           5500                                   Slurry Recycle, BPD                                                                            750    600            750                                    Combined Feed Temp., °F.                                                                510    506            431                                    Reactor Temp., °F.                                                                      920    920            928                                    Pegen. Dense Temp., °F.                                                                 1290   1275           1264                                   Regen. Dilute Temp., °F.                                                                1310   1300           1287                                   Flue Gas Temp., °F.                                                                     1290   1258           1320                                   Est. Additive "O"in Inv., wt. %                                                                0      6              5                                      Equilibrium Microactivity                                                                      65     60.sup.(1)     62                                     YIELD SUMMARY                                                                 Conversion, vol. %                                                                             69.0   64.7.sup.(1)   68.4                                   YIELDS                                                                        C.sub.2 minus, wt. %                                                                           1.7    1.2            1.2                                    C.sub.3, vol. %  1.4    1.1            2.0                                    C.sub.3 =, vol. %                                                                              5.8    6.9            6.6                                    iC.sub.4, vol. % 3.7    2.8            3.4                                    nC.sub.4, vol. % 0.5    0.9            1.1                                    C.sub.4 =, vol. %                                                                              7.0    7.9            8.3                                    C.sub.5 + gasoline (430°  F. E.P.) vol. %                                               57.3   53.1           55.4                                   Octane Number, Research                                                                        90.7   93.0           92.6                                   Total Gasoline + 77.8   76.8           79.2                                   Potential Alkylate, vol. %                                                    LCO (650° F. E.P.), vol. %                                                              17.6   19.1           17.3                                   Slurry, vol. %   13.4   16.2           14.3                                   Coke, wt. %      5.1    5.0            5.7                                    __________________________________________________________________________     .sup.(1) The activity loss, which resulted from lower than typical fresh      catalyst additions, was responsible for the lower conversion.            

The above examples clearly indicate that the catalytic compositions ofthe present invention which comprise octane enhancing FCC additivescontaining ZSM-5 zeolite may be used to produce significantly improvedyields of high octane gasoline fractions.

I claim:
 1. A catalytic cracking composition which comprises a separate particulate octane-enhancing additive component comprising ZSM-5 dispersed in an inorganic oxide matrix, and a particulate Y zeolite containing catalytic cracking catalyst component, comprising 15 to 60 percent by weight ultrastable y zeolite dispersed in an inorganic oxide matrix.
 2. The composition of claim 1 wherein the inorganic oxide matrix for said additive component and said cracking catalyst component is selected from the group consisting of silica-alumina cogels, silica, alumina, silica-alumina sol bound clay.
 3. The composition of claim 1 wherein the matrix of said ZSM-5 component comprises alumina sol and clay containing less than about 0.10 percent by weight Na₂ O.
 4. The composition of claim 1 wherein the ZSM-5 component comprises from about 5 to 50 weight percent of said composition.
 5. The composition of claim 1 wherein said composition has an average particle size ranging from about 50 to 85 micrometer.
 6. The composition of claim 1 wherein said matrix possesses a surface area of from about 20 to 400 m² /g and a pore volume of from about 0.15 to 0.60 cc/g. 